I'm also in the Z-Wave camp, with about 100 devices in my mesh. I still have some on Vera, so I actually have two Z-Wave networks active in my home. There's no question that Vera was a big contributor to problems with early Z-Wave experience. Even my oldest devices run well under Z-WaveJS. Multi-sensors that needed battery changes monthly on the Vera run for months without a change on Z-WaveJS (I suspect Vera's frequent restarts and "configuration" of each device each time are to blame). With the rapidly-declining stability of Ezlo's Vera cloud infrastructure, especially Alexa issues of late, I'm planning on being entirely off before March 1.
I've definitely had a few Z-Wave devices give up the ghost (or the radio); mostly older devices from lesser manufacturers of the time. The largest single group of switches and dimmers I have are all Leviton and around 11 years old, and I've only had one fail (radio died, otherwise functional). GE/Jasco seems to have held up second best among the high-age devices. Many of the other brands didn't make it two years, and those brands no longer exist, too. Everything I've bought in the last 4-5 years is holding on well. I think Zooz gets the award for most-improved. I didn't think much of them a few years ago (and told them so), but their more recent offerings have been stable and well-supported.
Part of the recent stability may be due to a campaign I went on several years ago (bored during Covid), where I found and fixed a number of small electrical problems in my house resulting in a variety of neutral issues (that is, issues with excessive current on the neutral wire). One of the most egregious was that our clothes dryer had been installed by the delivery guys to our four-wire connection with the neutral and ground bonded inside the dryer -- the bonding wire should have been removed for the four-wire service. This resulted in some fairly high circulating neutral and ground currents throughout the house, and in combination with other problems found (loose neutral or ground wires at receptacles, for example) was potentially hazardous and may have led to the failure of those less-robust devices. As I said, the last few years, I don't recall replacing any devices, so I've either eliminated a source of induced failure, culled out all of the weak, or both. I also have whole-house surge protection on my main panels. When my Internet was cable-carried (it no longer is), I had surge/lighting protection at the entrance.
I'm not enthusiastic about WiFi as an HA protocol for a few reasons: power demand, crowded bands, and user knowledge/security. While I love the simplicity of the Shelly WiFi-based devices and use them without reservation, they do not compare in battery life to even the oldest of my Z-Wave devices (well, those no longer on the Vera). The powered devices are fine. Powering many WiFi devices also seems to be "unevolved" -- Shelly gives you terminal connections for line voltage when powered; most others are USB micro or C at 5V with a wall wart, which truly sucks, and finding small UL-listed power supplies that can (and must be) safely installed in a US single-gang box or other enclosure is a nuisance and would make an insurance adjuster throw down his clipboard and walk out. WiFi generally is in increasingly crowded bands. In my neighborhood, the list of WiFi networks I see anywhere in my home that are at -60db or higher (i.e. strong) is long. While it used to be that unsophisticated users would simply crowd onto whatever preconfigured channel their router used by default and I could avoid them by changing channels, newer APs and firmware seek out the less-crowded channels automatically and spread out, so now every channel has a dozen competing networks at 2.4Ghz (relatively few I've found can do 5Ghz). Z-Wave's band has actually become less crowded over time (my neighbors finally abandoned their 20-year old cordless phones, I guess). Configuration and security also becomes an issue: rare is the home user that understands that IoT devices should be isolated from the rest of the network. Their eyes glaze over when you talk about VLANs, firewalls, and DMZs. They don't understand IP addressing, and will use the default /24 subnet their router offers and the small dynamic DHCP pool until the day they add that last Shelly device and now the wife's phone can't get an IP address when she comes home, etc. They will run their vendor-supplied AP at 100% with half-a-dozen 4K WiFi camera streams and wonder why their "Internet" is always slow (they don't even understand the difference between their Internet access and their WiFi network). There's a learning curve to building a solid, secure IP network with WiFi that most users have been shielded from forever and (were told) needed to know nothing about, but if you're going to start putting dozens of IP/WiFi devices on your home network, you'd better learn it and know it and do the work it takes to do it right at scale, or it will bite you hard from the inside or worse, the outside, soon and often.
I've got some BLE in my network as well, and it works well for its purpose (mostly presence sensing). I remain curious, even intrigued, but...
The biggest issue I find, and what I would guess-timate is the biggest barrier to finding a "one protocol to rule them all" today, is that there are no manufacturers that cover the full spectrum of required devices on a single protocol. Nobody makes everything you want, regardless of protocol. So we're left to find the best of breed in each category. I don't see that changing any time soon, or really, ever. The manufacturers follow the money. Smaller manufacturers like Zooz will make a good business out of filling holes that the big guys don't want to address (looking at the ZEN-32 for example). The big manufacturers will always make what they can sell the most, like switches and dimmers.
Matter, HomeBridge, and the like... they are effectively controlled by large corporations that are explicitly disinterested in working with small developers. Claiming open source while you maintain a closed, expensive, and opaque certification process doesn't fly for me. Z-Wave, admittedly, shares some of these ills in its proprietary history, but has been evolving to increasingly open over the last five years, with multiple vendors now producing silicon and that competition driving lower cost to implement. Z-Wave is also pretty much a single-interest ecosystem, where Google, Apple, Amazon, Samsung, and others involved in the likes of Matter and HomeBridge have many areas of research and development, and have been shown to quickly and suddenly divest themselves of technology they decide isn't worth continued effort. The players here have been bad actors in the past; I have no reason to believe they will behave differently in future.
Like others have said, beware the cloud. Eschew the cloud. It's sometimes a necessary, unavoidable evil, but you'd best minimize it.
